The two common denominators for battery life are on-screen time & quality of data/network connection.
If it were me,I'd stay w/VZW & the unlimited data,provided the network quality is up to par in the area(s) you'll be frequenting.
Phones come & go & are only as good as the network you're on.
With that said & if you've already decided to jump ship to AT&T,GSM network (AT&T/T-MOBILE) phones are reportedly better on the battery VS their CDMA counterparts (VZW/SPRINT).
ENGADGET has a review comparing the different networks performance,including battery life & the AT&T version fared well in their test:
HTC One for AT&T and Sprint: what's different?
Here's the excerpt from the review regarding battery life:
One of the reasons Engadget runs separate mini-reviews for US versions of phones is that while the overall design and camera performance might remain the same, battery life can often vary from one network to another. Indeed, we noticed some slight differences after putting the US models through their paces. While the 2,300mAh battery in the global model lasted six and a half hours in our usual rundown test (video looping, brightness fixed at 50 percent, etc.), our AT&T review unit lasted an average of seven hours and 29 minutes, besting the global model by about an hour. As for real-world use, the AT&T model carried on like a champ, lasting through a full day of maps use, podcasts, photo-taking, Facebook, Twitter, app downloads and speed tests. Even after eight hours, we still had about half a charge left. On the Sprint model, meanwhile, we achieved similar runtime of seven hours and five minutes in the same standardized rundown test.
After getting a production model of the SPRINT variant,ENGADGET updated the review to add the following:
Update: After testing a final, production-grade version of the Sprint model, we've updated our review with conclusive battery life results. It lasted seven hours and five minutes in our standard rundown test, similar to both the AT&T and global versions.
Please keep us posted & visit the actual users thread for your thoughts on the HTC ONE:
Real world reviews & comments from actual users